💧 epanet-js: Open Source Meets Hydraulic Simulation

Tom introduces epanet-js, a browser-based web application that merges modern web mapping with the EPANET hydraulic simulation engine—a tool used to model water distribution systems. Built by Luke Butler and Sam Payá from Iterating, epanet-js is designed for professionals managing water utilities, helping them simulate pipe networks, pressures, and flow dynamics.

What makes this project remarkable is its open-source lineage. Tom previously created Placemark, a general-purpose map editing tool. Though the business didn’t succeed, he open-sourced it under the MIT license, allowing others to build freely—even commercially. epanet-js uses Placemark’s codebase and has contributed upstream improvements, despite no obligation to do so.

🧠 Why It Matters

• Legacy through openness: Tom celebrates the idea that his code lives on in a niche where it truly fits.

• Functional Source License: epanet-js itself is released under a license that makes new contributions open source after two years.

• Browser-native simulation: It runs hydraulic simulations in-browser using WebAssembly, competing with legacy software that costs ~$16,000/year and runs only on Windows.

🎉 Final Thought

Tom calls epanet-js a “radical improvement” over traditional tools and encourages anyone in hydraulic simulation to give it a try. It’s a story of open-source generosity meeting real-world utility.